Drying plant



May 20, 1958 H. F. A. RYDIN 2,835,051

DRYING PLANT Filed March 28, 1955 4 Sheets-Sheet 1 ATTORNEYS May 20, 1958 H. F. A. RYDIN 2,835,051

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DRYING PLANT Filed March 28, 1955 4 sheets-sheet 4 ATTORNEYS United States Patent() n 2,835,051 DRYING PLANT Hans Folke Axel Rydin, Djursholm, Sweden, assignor to Stockholms Superfosfat Fabriks Aktiebolag', Stockholm, Sweden, a company of Sweden ApplicationV March' 28, 1955", Serial No. 497,320

' 4 claims. (cl. .a4-174) The present invention concerns an arrangement in drying plants consisting of a vertical shaft in which are placed two concentric perforated screens between which the material to be dried can slide down while being affected by a mainly horizontal gas stream through the screens.

The main problem in drying plants without rotary parts is how to prevent any aggregations of the material to be dried from sticking in the dryer, where they might be superheated and ignite the material in the body of the dryer.

That risk is particularly serious when drying coke, which always contains a good deal of dust. Taking this problem into full consideration, the present invention has no impeding parts in the drying zone between the gas-transmitting screens and the outlet cone, nor does any part of the hotdrying gas pass through thel material assembling ou the inlet cone.

The invention is characterized by the two screens, open at the bottom to their full diameters, being suspended in the upper portion of the shaft above a common outlet cone, the upper diameter of which exceeds that of the outer screen. A free passage down into the outlet cone is thus ensured between the screens for the material to be dried.

One form of drier according to the present invention,

v which form is specially designed for coal and coke, will be described below in greater detail with reference to 'the appended drawings, of which:

Fig. 1 is a vertical sectional view of my drying plant;

Fig. 2 is a sectional view taken along line 22 of Fig. l;

Fig. 3 is a sectional view taken along line 3-3 of Fig. 1;

Fig. 4 is a detailed sectional View of the means 'for securing the feed cone and the cylindrical outer screen to the ring shaped gas conduit of the cylindrical shaft;

Fig. 5 is a detailed view of the bolt means for securing the sheet iron cylinder to the ring-shaped gas conduit;

Fig. 6 isa detailed View of the bolt means for securing theupper end of the sheet iron cylinder to the feed cone;

Fig. 7 is a detailed sectional View showing the structure of the inner and outer screens; and

Fig. 8 is a sectional view taken along line 8 8 of Fig. 7. V

This drier consists of a cylindrical shaft 1, the lower part of which forms a cone 2 with an outlet opening. Inside the shaft are two concentric perforated screens 4 and 5, between which the material to be dried falls by gravitation down into the outlet cone 2. These screens may be made of round vertical iron bars set relatively far apart, seeing that it matters little if some coke should pass through the screens; the coke will in any case drop into the same outlet cone. The screens may also be made of xed horizontal rings inclined inwardly and outwardly respectively in relation to the direction in which the coke is falling, thus preventing coke particles from passing through the interstices.

The outer screen 5 is supported at the 'top by an unperforated sheet-iron cylinder 3v connected to the ringshaped conduit 6 by bolts, welding or other suitable means. The inner screen 4 is also supported at the top by a sheet-iron cylinder 11i, the upper part of which is attached underneath a feed cone 7, the bottom rim of which projects outside the sheet-iron cylinder 11. so as to collect the coarser coke particles nearest to the screen. The sheet-iron cylinders must be of a height exceeding the space between the screens, so that the coke will form a seal preventing any gas escaping upwards. The feed cone 7 is suspended from the conduit 6 by a number of gas exhaust tubes 8 projecting radially from the cone and opening into the ring-shaped gas conduit 6. VThe lengthening sheet-iron cylinder 3 above screen 5 is attached outside the inner edge of the said gas conduit 6 in order to collect the coarser coke particles nearest to the screen. From the gas conduit the gas is drawn by a fan to a chimney 18. A removable top cone 9 is provided on the feed cone 7 for inspection of the chamber 17 inside the inner screen 4.

According to the present invention, the inner screen is thus closed at the top by the tight feed-cone suspended by the gas exhaust tubes, but these tubes pass through the material suciently far away from the drying zone to eliminate any risk of the temperature of the exhaust gases-which incidentally is much lower than that of the drying gases-overheating the material and so causing ignition. Note also that, for additional security against the said risk of ignition, the drying zone between the screens is according to this invention left cornpletely free for the passage of the material,

The top sides of the gas tubes 8 are wedge-shaped, sloping more steeply than the angle of repose, so that no breeze can be left on the tubes to cause ignition. Besides functioning as a collecting chamber for exhausted drying gas, the ring-shaped conduit 6 serves as an annular girder carrying the screens 4 and 5.

The shaft wall is provided with ports 16 to 'admit the drying gas, which is carried to them by a fan 15 through a sheet-iron conduit 14 and evenly distributed in chamber 13 round the outer screen 5. The shaft wall may of course also be constructed so as to perform thevfunctions of the outer screen. The drying gas thus passes through the ports 16, the outer screen 5, the coke layer and the inner screen 4 to the chamber 17, and then is removed by suitable exhaust means through the gas tubes 8 and the exhaust conduit 18.

The capacities of the fan 15 and of the suction fan in the chimney should be adjusted to prevent any upward or downward escape of the drying gas.

As the chamber 17 inside the inner screen 4 is directly evacuated by the suction fan, supplementary evaporation will also take place from the surface of the material down in the outlet cone.

I claim:

l. Drying apparatus for granular materials comprising an open-ended vertical cylindrical shaft, said shaft having a horizontally-arranged radially-inwardly directed annular conduit adjacent the upper end thereof defining a centrally-located substantially-circular inlet opening, and a conically-convergent portion at the lower end thereof defining an outlet opening; an upwardly-convergent feed cone in said shaft inlet opening and spaced from the inner wall of said annular conduit to form a feed passage therebetween; a plurality of gas exhaust tubes each connected at one end to and in communication with said annular conduit and at the other end to said feed cone to rigidly secure said feed cone in said inlet opening; two concentrically-arranged' Vertical cylindrical screens within said shaft, said screens being open to their full diameters at their lower ends above said outlet Patentedl May 20, 1958 cone; means for suspending the inner one of said screens at its upper end from said feed cone; means for suspending the outer one of said screens at its upper end from said annular conduit; means for passing a drying gas stream radially inwardly through said outer and inner screens so that the granular material is dried as it passes downwardly between the screens from the inlet to the outlet of the shaft; and means in communication with said annular conduit for withdrawing the drying gases from the interior of the inner screen, through said gas exhaust tubes, and from said annular conduit.

2. Apparatus as defined in claim 1 wherein said outer screen has a diameter greater than the inner diameter of the annular conduit.

3. Apparatus as defined in claim 2 wherein said means for suspending the outer screen includes an imperforate cylinder having a diameter substantially equal to the -di ameter of said outer screen, said imperforate cylinder 4 being connected at its lower extremity to the upper extremity of said screen and at its upper extremityto said annular conduit.

4. Apparatus as defined in claim 1 wherein said means for suspending said inner screen includes an imperforate cylinder having a diameter substantially equal to the diameter of said inner screen.

References Cited in the le of this patent UNITED STATES PATENTS 685,336 Leroy et al. Oct. 29, 1901 691,209 Tweedale et al. Jan. 14, 1902 1,547,400 Kimber July 28, 1925 1,718,243 Lindhard June 25, 1929 2,554,435 Weber May 22, 1951 FOREIGN PATENTS 717,052 Great Britain Feb. 4, 1942 

